Laser thermometer

ABSTRACT

Method and Apparatus are provided for visibly outlining the energy zone to be measured by a radiometer, the method comprises providing a laser sighting device on the radiometer adapted to emit more than two laser beams against a surface whose temperature is to be measured and positioning said laser beams about the energy zone to identify said energy zone. The apparatus comprises a laser sighting device adapted to emit more than two laser beams against the surface and means to position said laser beams about the energy zone and to identify said zone. A primary laser beam is passed through or over a beam splitter or a diffraction grating and formed into a plurality of secondary beams which produce on the target surface a pattern which identifies the zone investigated with the radiometer. Laser light may be directed axially to illuminate the central area of the zone.

RELATED APPLICATIONS

This is a continuation application of pending application Ser. No.09/843,927 filed Apr. 30, 2001, which is a division of U.S. Ser. No.09/145,549 filed Sep. 2, 1998, now U.S. Pat. No. 6,267,500, which is adivision of U.S. Ser. No. 08/848,012 filed on Apr. 28, 1997 and now U.S.Pat. No. 5,823,679 issued Oct. 20, 1998. U.S. Ser. No. 08/848,012 is acontinuation-in-part application of both pending U.S. applications Ser.Nos. 08/764,659 filed on Dec. 11, 1996 now U.S. Pat. No. 5,823,678 and08/617,265 filed on Mar. 18, 1996 now U.S. Pat. No. 5,727,880 in thenames of Milton B. Hollander and W. Earl McKinley for Method andApparatus for Measuring Temperature Using Infrared Techniques, thelatter of which, is a continuation-in-part of U.S. application Ser. No.08/348,978 filed on Nov. 28, 1994, now U.S. Pat. No. 5,524,984 which inturn was a continuation application of then copending U.S. patentapplication Ser. No. 08/121,916 filed Sep. 17, 1993, now issued as U.S.Pat. No. 5,368,392, on Nov. 29, 1994.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for moreaccurately measuring the temperature of a surface at a measurement spot,using infrared measurement techniques and, more particularly, to such amethod and apparatus which utilizes a laser sighting device which isadapted to project at least a visible circumscribing intensive lightdistribution circle from a laser sighting beam or beams for more clearlyoutlining, identifying and defining location, position, area, size andthe periphery of the energy zone from which the temperature is measured.Generally speaking, this has been accomplished by directing andpositioning the laser beam or beams about the periphery of the energyzone or measurement spot by use of three or more stationary laser beamswhich are focused on the periphery of the energy zone; or by the use ofa controlled single laser beam directed towards three or morepredetermined locations on the periphery of the energy zone. In thealternative embodiment, a single laser beam may be rotated around theperiphery of the energy zone using, for example, slip rings. In anotherembodiment, the single rotating laser may be pulsed on and off in asynchronized manner in order to produce a series of intermittent linesoutlining the energy zone, thus increasing the efficiency of the laserby concentrating its total wattage in a smaller area, causing a brighterbeam. Further, the circumscribing beam or beams may be used inconjunction with the additional beam directed at or near and defining acentral spot, or larger central area, of the energy zone or measurementspot.

In yet another method and embodiment, at least one laser beam issubdivided by passing it through an optical means such as a beamsplitter or diffraction grating, for example, into a plurality of threeor more subdivision beams which can form a pattern of illuminated spotareas on a target whose energy zone is to be investigated with aradiometer.

2. Description of the Prior Art

Remote infrared temperature measuring devices (commonly referred to asinfrared pyrometers or radiometers) have been used for many years tomeasure the temperature of a surface from a remote location. Theirprinciple of operation is well known. All surfaces at a temperatureabove absolute zero emit heat in the form of radiated energy. Thisradiated energy is created by molecular motion which produceselectromagnetic waves. Thus, some of the energy in the material isradiated in straight lines away from the surface of the material. Manyinfrared radiometers use optical reflection and/or refraction principlesto capture the radiated energy from a given surface. The infraredradiation is focused upon a detector, analyzed and, using well knowntechniques, the surface energy is collected, processed and thetemperature is calculated and displayed on an appropriate display.

Examples of such infrared radiometers are illustrated at pages J-lthrough J-42 of the Omega Engineering Handbook, Volume 2B. See, also,U.S. Pat. No. 4,417,822 which issued to Alexander Stein et al. on Nov.29, 1983 for a Laser Radiometer; U.S. Pat. No. 4,527,896 which issued toKeikhosrow Irani et al. on Jul. 9, 1985 for an InfraredTransducer-Transmitter for Non-Contact Temperature Measurement; and U.S.Pat. No. 5,169,235 which issued to Hitoshi Tominaga et al. for RadiationType Thermometer on Dec. 8, 1992. Also see Baker, Ryder and Baker,Volume II, Temperature Measurement in Engineering, Omega Press, 1975,Chapters 4 and 5.

When using such radiometers to measure surface temperature, theinstrument is aimed at a target or “spot” within the energy zone on thesurface on which the measurement is to be taken. The radiometer receivesthe emitted radiation emanating from a measurement spot on an object ofmeasurement through the optical system and is imaged and focused upon aninfrared sensitive detector which generates a signal which is internallyprocessed and converted into a temperature reading which is displayed.

The precise location or position of the energy zone or measurement spoton the surface as well as its size and area are extremely important toinsure accuracy and reliability of the resultant measurement. It will bereadily appreciated that the field of view of the optical systems ofsuch radiometers is such that the diameter of the energy zone increasesdirectly with the distance to the target. The typical energy zone ofsuch radiometers is defined as where 90% of the energy focused upon thedetector is found. Heretofore, there have been no means of accuratelydetermining the perimeter, area, size and location of the actual energyzone unless it is approximated by the use of a “distance to targettable” or by actual physical measurement.

Target size and distance are critical to the accuracy of most infraredthermometers. Every infrared instrument has a field of view (FOV), anangle of view in which it will average all the temperatures which itsees. Field of view is described either by its angle or by a distance tosize ratio (D:S). If the D:S=20:1, and if the distance to the objectdivided by the diameter of the object is exactly 20, then the objectexactly fills the instrument's field of view. A D:S ratio of 60:1 equalsa field of view of 1 degree.

Since most infrared thermometers have fixed-focus optics, the minimummeasurement spot occurs at the specified focal distance. Typically, ifan instrument has fixed-focus optics with a 120:1 D:S ratio and a focallength of 60″ the minimum spot (resolution) the instrument can achieveis 60 divided by 120, or 0.5″ at a distance of 60″ from the instrument.This is significant when the size of the object is close to the minimumspot the instrument can measure.

Most general-purpose infrared thermometers use a focal distance ofbetween 20″ and 60″ (50 and 150 cm); special close-focus instruments usea 0.5″ to 12″ focal distance. See page Z54 and Z55, volume 28, The OmegaEngineering Handbook, Vol. 28. In order to render such devices moreaccurate, laser beam sighting devices have been used to target theprecise center of the energy zone. See, for example, pages C1-10 throughC1-12 of The Omega Temperature Handbook, Vol. 27. Various sightingdevices such as scopes with cross hairs have also been used to identifythe center of the energy zone to be measured. See, for example, PagesC1-10 through C1-21 of The Omega Temperature Handbook, Vol. 27.

The use of a laser to pinpoint only the center of the energy zone doesnot, however, provide the user with an accurate definition of the actualenergy zone from which the measurement is being taken. This inabilityfrequently results in inaccurate readings. For example, in cases wherethe area from which radiation emits is smaller than the target diameterlimitation (too far from or too small a target), inaccurate readingswill occur.

One method used to determine the distance to the target is to employ aninfrared distance detector or a Doppler effect distance detector or asplit image detector similar to that used in photography. However, theexact size of the energy zone must still be known if one is to have anydegree of certainty as to the actual area of the surface being measured.This is particularly true if the energy zone is too small or the surfacewhich the energy zone encompasses is irregular in shape. In the casewhere the surface does not fill the entire energy zone area, thereadings will be low and, thus, in error.

Similarly, if the surface is irregularly shaped, the readings will alsobe in error since part of the object would be missing from the actualenergy zone being measured.

Thus, the use of a single laser beam only to the apparent center of theenergy zone does not insure complete accuracy since the user of theradiometer does not know specifically the boundaries of the energy zonebeing measured.

As will be appreciated, none of the prior art recognizes this inherentproblem or offers a solution to the problems created thereby.

Proposals have been made in the prior art for indicating an energy zonearea of a target surface by means visible to the eye.

A first kind of such indication utilizes multi-spectral light, asevidenced for example in the Japanese Publication No. S57-22521 whichteaches the use of an incandescent light source to outline an energyzone at the target. Japanese Publication No. 62-12848 suggests a similaruse of multi-spectral light to outline an energy zone at the target.Reference is made to Japanese case JP 63-145928.

Further, U.S. Pat. No. 4,494,881 EVEREST also suggests using amulti-spectral light source together with a beam splitter arrangementwhich permits the infra-red received beam and the multi-spectral lightto utilize the same optical arrangement. EVEREST teaches the use of avisible light source such as an incandescent lamp or strobe light whichis projected against the target surface, the temperature of which is tobe measured. This adds additional energy to the same energy zone wherethe temperature measurement is to be taken, and this destroys accuracy.When EVEREST uses a beam splitter, the incandescent light beam causesthe beam splitter to act as a radiator of infrared energy. When EVERESTuses a Fresnel lens, the light tends to elevate the temperature of theFresnel lens, which in turn reflects back to the infra-red detector.

This manner of indication, utilizing incoherent multi-spectral light,has the disadvantage amongst others that the multi-spectral light itselfhas a heat factor which can cause incorrect reading by the energydetecting means of the apparatus.

A laser is Light Amplification by Stimulated Emission of Radiation. Thisdevice was invented in 1960 to produce an intense light beam with a highdegree of coherence. Atoms in the material emit in phase. Laser light isused in holography. A light beam is coherent when all component waveshave the same phase. A laser emits coherent light, but ordinary electricincandescent light is incoherent in which atoms vibrate independently.

It is not possible simply to substitute a laser for an incandescentlight source, because the incandescent beam is incoherent in nature, sothat when projected parallel and in close proximity to the boundaries ofthe invisible infra-red zone, incandescent light inside the infra-redzone is reflected as heat energy. Moving the incandescent beam well awayfrom the infra-red zone clearly does not permit accurate delineation ofthe target zone.

A second kind of energy zone indicator utilizes coherent laser light, asevidenced for example in U.S. Pat. No. 4,315,150 of DERRINGER, which isdirected to a targeted infrared thermometer in which a laser is providedto identify the focal point, i.e., the center, of the energy zone, butthere is nothing in DERRINGER to suggest causing more than two laserbeams to outline the energy zone.

U.S. Pat. No. 5,085,525 BARTOSIAK ET AL teaches use of a laser beam toprovide a continuous or interrupted line across a target zone to beinvestigated, but there is no suggestion to outline a target zone, norto indicate a central point or central area of the target zone.

German patent publications of interest include:

DE-38 03 464

DE-36 07 679 to a laser sighting device.

DE-32 13 955 to a beam splitter and to dual laser beams to indicateposition and diameter of the energy zone

All of the above noted prior art is hereby incorporated into this caseby reference thereto.

SUMMARY OF THE INVENTION

Against the foregoing background, it is a primary object of the presentinvention to provide a method and apparatus for measuring thetemperature of a surface using infrared techniques.

It is another object of the present invention to provide such a methodand apparatus which provides more accurate measurement of the surfacetemperature than provided by the use of techniques heretofore employed.

It is yet another object of the present invention to provide such amethod and apparatus which permits the user visually to identify thelocation, size and temperature of the energy zone on the surface to bemeasured.

It is still yet another object of the present invention to provide suchmethod and apparatus which employs a heat detector and a laser beam orbeams for clearly outlining the periphery of the energy zone of thesurface.

It is a still further object of the present invention to provide amethod and apparatus which permits the use of a single laser beam whichis subdivided by passing it through, or over, an optical means such as abeam splitter, holographic element or a diffraction grating, aligned tobe illuminated by said single laser beam, thereby to form a plurality ofthree or more subdivision beams which provide a light intensitydistribution pattern where they strike a target whose energy zone at ameasurement spot is to be investigated.

It is still further object of the invention to provide a method andapparatus which utilizes not only a beam or beams for outlining theenergy zone, but also an additional beam or beams directed at andilluminating an axial central spot, or larger central area, of theenergy zone.

For the accomplishment of the foregoing objects and advantages, thepresent invention, in brief summary, comprises a method and apparatusfor visibly outlining the energy zone to be measured by a radiometer.The method comprises the steps of providing a radiometer with a detectorand a laser sighting device adapted to emit at least one laser beamagainst a surface whose temperature is to be measured and controllingsaid laser beam towards and about the energy zone to outline visiblysaid energy zone. The beam is controlled in such a fashion that it isdirected to three or more predetermined points of the target zone. Thiscan be done mechanically or electrically.

Another embodiment of this invention employs a plurality of three ormore laser beams to describe the outline and optionally also the centerof the energy zone either by splitting the laser beam into a number ofpoints through the use of optical fibres or beam splitters or adiffraction device or the use of a plurality of lasers. One embodimentof the apparatus comprises a laser sighting device adapted to emit atleast one laser beam against the surface and means to rotate said laserbeam about the energy zone to outline visibly said energy zone. Thisrotation can be by steps or continuous motion.

Another embodiment consists of two or more stationary beams directed todefine the energy zone. The three or more laser beams could each bederived from a dedicated laser to each beam or by means of beamsplitters. This can be accomplished by mirrors, optics, a diffractiongrating, and fibre optics.

Another embodiment consists of a laser beam splitting device that emitsone laser beam which is split into a plurality of three or more beams,by a diffraction grating, for example, to outline the energy zone andoptionally to indicate a central spot or larger central area of theenergy zone.

In a still further embodiment, the temperature measurement devicecomprises a detector for receiving the heat radiation from a measuringpoint, spot or zone on an object of measurement under examination.Integral to the equipment is a direction finder, i.e. a sighting deviceusing a laser beam as the light source and incorporating an opticalmeans such as a diffractive optic, i.e. a holographic component such asa diffraction grating, or a beam splitter, with which the lightintensity distribution is also shown and the position and size of theheat source is indicated. The marker system relates to a predeterminedpercentage, e.g. 90%, of the energy of the radiated heat.

The method includes visually outlining and identifying the perimeter ofthe energy zone by projecting more than two laser beams to the edge ofthe 90% energy zone to mark out the limits of the surface area underinvestigation, for example, by a series of dots or spots which form apattern.

Two or more embodiments may be used together or alternately.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and still other objects and advantages of the presentinvention will be more apparent from the detailed explanation of thepreferred embodiments of the invention in connection with theaccompanying drawings, wherein:

FIG. 1 is a schematic illustration of the prior art type of radiometersusing laser sighting devices;

FIG. 2 is a schematic illustration of one embodiment of the presentinvention in which the laser beam is circumscribing the target zoneusing a mirror;

FIGS. 2A and 2B illustrate the manner in which the laser beam isrelocated in stepped fashion to identify the energy zone;

FIG. 3 is schematic illustration of an alternative embodiment of thepresent invention in which the laser is pivoted about a pivot point bythe use of mechanical motive means;

FIG. 4 is a schematic illustration of another alternative embodiment ofthe present invention in which the laser is directed through a magneticfield to identify the target zone;

FIG. 5 is a schematic illustration of another alternative embodiment ofthe present invention in which a number of individual laser beams areprojected so as to define the energy zone being measured;

FIG. 6 is a schematic illustration of another alternative embodiment ofthe present invention in which the laser is mechanically pivoted;

FIG. 7 schematically illustrates the positioning of fiber optics tocreate a pattern of the target zone with the laser beam;

FIG. 8 is a detailed sectional view of another alternative embodiment ofthe present invention in which the laser is mechanically pivoted aboutthe detector;

FIGS. 9A-C illustrate alternative configurations of the outlines whichcan be projected using the apparatus of the present invention;

FIG. 10 is a schematic illustration of an embodiment of the inventionwherein the laser is divided into a plurality of laser beams definingthe energy zone by the use of optical fibres.

FIG. 11 is a cross sectional side view of a laser sighting device whichmay be used in conjunction with a radiometer in which the laser isrotated using slip rings;

FIG. 12 is a side view illustrating a modified version of the lasersighting device of FIG. 11 with the sighting device mounted on aninfrared detector;

FIG. 13 is a side view illustrating still another modified version ofthe laser sighting device of the present invention;

FIG. 14 is a side view of yet another embodiment of the invention inwhich the laser sighting device utilizes twin laser beams provided onopposite sides of an infrared detector;

FIG. 15 is a front view of the embodiment of FIG. 14;

FIG. 16 is a top view of the embodiment of FIGS. 14-15;

FIG. 17 illustrates the intermittent lines formed by a laser which ispulsed on and off in a synchronized manner;

FIG. 18 is an illustration in partial section of a preferred embodimentof the invention in which the laser sighting device utilizes a singlelaser beam which is divided and spread into a plurality of individualbeams by means of a diffraction grating;

FIG. 19 is a diagram to show a pattern of dots of laser light, formed ona target area, as a result of impingement of the individual beamsresulting from sub-division of the single beam of the laser;

FIG. 20 is a diagram to show a modification wherein the radiometer isarranged on the axis of the laser beam.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS

Traditionally, prior art radiometers have long employed laser sightingdevices and direction finders to assist in the proper aim and alignmentof the instrument. FIG. 1 illustrates and direction finders theoperation of traditional, prior art, hand held radiometers. Such aradiometer, referred to generally by reference numeral 10, includes alaser sight scope 12 which emits a laser beam 14 to a spot or target 18on the surface 20 whose temperature is to be measured. This spot 18 islocated in the center of the energy zone “E” which is to be measured bythe radiometer 10. The radiometer 10 includes a detector 16 which isconnected to conventional internal circuitry and display means (notshown) for conversion, calculation and display of the temperature of thesurface 20 calculated indirectly from the energy radiated from thesurface within the energy zone E. Such energy is radiated in straightlines in all directions away from the surface 20 and captured with thedetector 16 on the radiometer 10. Using infrared radiation principles,the radiometer is thus able to capture and measure the infrared energyin the energy zone E and to display the surface temperature thereof.

The actual size and shape of the energy zone E is determined by theoptics of the radiometer and the distance between the radiometer and thetarget. Each radiometer has a defined angle of vision or “Field of view”which is typically identified in the instrument's specification sheet.The size of the energy zone E is predetermined when the field of view isknown in conjunction with the distance to the target. Obviously, thefurther the radiometer is held from the target (i.e., the greater thedistance), the larger the energy zone E.

This can be expressed in a “distance to spot size zone”. For example,with a “distance to spot size zone” of 40:1 the periphery of the energyzone would have a 1″ diameter at a distance of 40″ or, at a distance of20″ the diameter of the energy zone would be ½″. The manufacturer of thepyrometer usually provides field of view diagrams for determining theenergy zone at specific distances.

As can readily be appreciated, however, such laser aiming devices aremerely able to identify the center of the energy zone being measured andnot the outer periphery, as distinct from the diameter, of the actualenergy zone from which the measurement is being taken. The further awayfrom the surface the radiometer 10 is positioned, the larger the energyzone E. Thus, depending upon the size and configuration of the surface20, the actual energy zone E may, conceivably, include irregular shapedportions of the surface 20 or even extend beyond the edges of thesurface. Of course, in such instances, the resultant measuredtemperature would be inaccurate. Without knowing the outer perimeter ofsuch energy zone E, the user of the radiometer 10 would have noknowledge of such fact and the resultant readings could be inaccurate.

The present invention provides a means for visibility defining theenergy zone E so that the user of the radiometer 10 can observe theactual energy zone being measured to determine where it falls relativeto the surface being measured. In the various embodiments of thisinvention, a fine laser line or lines is projected against the surfacebeing measured and such line or lines is positioned so as to encompassthe periphery of the energy zone E. Of a rotating laser beam isemployed, positioning can be effected, alternatively by moving eitherthe laser itself or the laser beam emitted from the laser or from alaser beam splitter.

If the perimeter of the energy zone E cold be identified on the objectby the movement of the laser beam in a path about the circumference ofthe energy zone E, the user would be able quickly and accurately todetermine if the energy zone from which the measurement was being takenwas fully on the surface to be measured and whether its surface was ofthe type which would provide an otherwise accurate measurement.

The periphery of the energy zone E is identified as a function of thestated “field of view” of the particular radiometer as identified in itsspecifications and the distance between the radiometer and the target.Identification of the size and shape of the energy zone is easily doneusing conventional mathematical formulae. Once identified, the laserbeams are then projected about the periphery of the energy zone E inaccordance with the methods and apparatus hereinafter described. Onesimple “aiming” approach is to project the laser beam at the same angleas the field of view of the radiometer emanating from the same axis or,alternatively, by mechanically adjusting the laser beam angle inaccordance with the “distance to spot size ratio” calculations. Ineither event, the periphery of the energy zone E would be identified bythe laser beams.

FIG. 2 illustrates a first embodiment of the present invention in whichthe laser aiming device 12 emits a laser beam 14 which is aimed at amirrored surface 30 which is positioned in front of the laser beam 14.The mirror 30 is rotated using motive means 32 so as to rotate the beamin a circular fashion to define the energy zone E on the surface beingmeasured. Alternatively, the mirror 30 can be rotated by vibratory meansor by the application of a magnetic field (not shown). Rotation of themirror 30 should be a refraction angle which corresponds to the 90%energy zone E thereby permitting the laser beam 14 to rotate about theperiphery of the energy zone E and thereby making it visible to the userof the radiometer 10.

It should be appreciated that the laser aiming device 12 may be anintegral part of the radiometer 10 or, alternatively, a separate unitthat may be mounted on or near the radiometer 10.

Alternatively, a prism can be used in place of the mirror 30 withpredetermined angles to cause the prism to function as the reflectingmirror surface and, thereby, direct the laser beam about the perimeterof the energy zone.

FIGS. 2A and 2B illustrate the manner in which laser beams can be usedto outline the energy zone E on the surface to be measured. It isimportant that rotation of the beam 14 be carefully controlled so thatrotation is at a speed which can be visually followed. This will permitfull beam intensity. As illustrated in FIGS. 2A and 2B, the laser beamis rotated about the energy zone E through a series of steps with thelaser beam being permitted to remain in each step for at least onehundredth of a second before moving to its next position. This isaccomplished by creating a plurality of steps E-1, E-2, etc., around theenergy zone E. The laser beam 114 would stop at each step for thepredetermined period of time to permit the beam to be observed beforemoving to the next step.

FIG. 3 illustrates another embodiment of the present invention in whichthe laser 112 itself is rotated or displaced so as to scribe a circle orother closed figure which defines the energy zone E by mechanicallypivoting the laser 112 about pivot point 120 using motive means 132.Alternatively, the laser 112 can be rotated by a vibratory means (notshown) or by the application of a magnetic field (not shown). Rotationof the laser 112 should, however, be at a refraction angle whichcorresponds to the 90% energy zone E thereby permitting the laser beam114 to rotate about the periphery of the energy zone E to make itvisible to the user of the radiometer 10.

In FIG. 4, the laser 212 is rotated about a pivot point 220 by theapplication of a magnetic field 225 so as cause the emission of thelaser beam 214 around the periphery of the 90% energy zone E to make thebeam visible to the user of the radiometer 10. In such embodiment, means(not shown) are provided for modifying the magnetic field 225 tocorrespond to the 90% energy zone so as to permit the laser to berotated accordingly.

In FIG. 5, the laser 312 has at least two components 312A and 312B whichproduce at least two individual laser beams 314A and 314B about thedetector 316. These at lest two individual beams 314A and 314B aredirected to the surface 320 being measured at the perimeter of theenergy zone E rather than at the center of the energy zone E. Throughthe use of a number greater than two of such laser beams, thesignificant energy zone E becomes clearly identified rather than merelythe center of the E zone. If desired individual lasers can be used orlaser splitting devices can be used to split a single laser beam. Adiffraction device such as a grating or holographic component may beused to form multiple beams. Two lasers may be adapted to project a pairof laser beams on different sides of said energy zone.

FIG. 6 illustrates yet another embodiment of the present invention inwhich the laser 412 is mechanically pivoted in a circular fashion aroundthe detector 416 so as to emit a laser beam 414 in a circular path onthe surface (not shown) thereby defining the energy zone E. Laser 412 ispivotally mounted on pivot bearing 420 provided on connecting arm 421.Arm 421 is mounted on pivot bearing 424 which is rotated by motor 422.In such a manner, the laser beam 414 emitted from the laser 412 rotatesabout and outlines the energy zone E on the surface from which thetemperature is being measured.

The rotation of the laser beam may be effected using beam splitter orfiber optic techniques as shown in FIG. 7 in which the laser beam isprojected through fiber optic means 501. In such manner, the beams fanout from the laser source and encircle and thereby define the energyzone E. By the use of a sufficient number of fiber optics, one canoutline the circumference of the target area E with a light ring or by aring of dots. This can be accomplished by as few as two fibers 501positioned 180 degrees apart since the pick up pattern would becircular. Further fiber optic means may serve to direct a laser beamonto a central spot, or larger central area, of the energy zone.

FIG. 8 illustrates still another means of effecting rotation of thelaser beam 614 emitted from laser 612. In this manner, the laser beam614 is directed against a rotating flat surface mirror 630 where it isreflected against a plated plastic cone mirror 631. The reflected beamis then projected to the surface and defines the perimeter of the energyzone E. The flat mirror 630 is driven by motor 622. In such manner, thelaser beam 614 rotates about the circumference of the energy zone E onthe surface being measured. The mirrors are positioned at such an anglethat the laser projection is at the same angle as the infrared detectorpickup angle.

It will, of course, be appreciated that the energy zones E may assumeconfigurations other than the circular configuration shown in FIGS. 1-8.FIGS. 9A-C illustrate alternative square (FIG. 9A), rectangular (FIG.9B), and triangular (FIG. 9C) configurations for the light patternswhich may be accomplished using the means of the present invention. Aclosed configuration is preferred. This may include three or more dotsor spots.

FIG. 10 illustrates a method for defining the energy zone where acircular configuration can be accomplished without rotation of the laserbeam wherein a plurality of fixed optical fibers positioned to project anumber of spots is employed. In this figure, a fixed laser 712 projectsa beam 713 which is split into a plurality of beams 714 by a bundle ofoptical fibers 715 in order to project a pattern 716 onto the surfacedefining the energy zone E. Additional configurations may also be used,if desired. A diffraction means will also produce a pattern.

Referring to FIG. 10, the means for projecting a plurality of laserbeams (the bundle 715) will likewise include optical fibers arranged toproject a laser beam axially so as to cause the plurality of laser beamsto identify and define both the center and the periphery of the energyzone, e.g. by providing a single center spot or larger central area onthe surface to be measured.

FIGS. 11-12 illustrate further embodiments of the present invention inwhich the laser is adapted to be rotated by the use of slip rings andcounter weights. For example, FIG. 11 illustrates one laser sightingdevice 1000. Laser sighting device 1000 can be provided as an integralunit in combination with an infrared detector (not shown) or,alternatively, may be self contained as a removable sighting devicewhich can be attached to and removed from infrared detectors.

The laser sighting device 1000 of FIG. 11 includes a laser 1012 poweredby power source 1018 which projects a laser beam 1014 against target.The laser 1012 is pivotally mounted about pivot 1020. Motor 1021 isprovided for powering the sighting device and causing the laser 1012 torotate. An external switch (not shown) may be provided to turn the motor1021 on and off and, as such, the rotation of the laser 1012. Upper andlower screw adjustments of 1013 and 1011, respectively, are provided forcontrolling the position of the laser 1012 and, more importantly, thedirection of the laser beam 1014. Upper screw adjustment 1013 is adaptedto be used during non-rotation while lower screw adjustment 1011 issuedduring rotation of the laser 1012.

The laser 1012 is powered with power source 1018. Slip rings 1016 areprovided to facilitate rotation of the laser 1012. Upper and lowercounterweights 1015A and 1015B, respectively are provided above andbelow the laser 1012 and a return spring 1019 is also provided.

The laser 1012 of the sighting device 1000 in FIG. 11 is adapted torotate about the pivot 1020 when driven by the motor 1021. Thus, thelaser 1012 is able to project a laser beam 1014 with a circle-typepattern against a target (not shown) During rotation, centrifugal forcewill act upon the counterweights 1015A and 1015B causing the laser 1012to tilt. The angle at which it tilts can be controlled by the screwadjustment 1013 and 1011. The angle is adjusted to correspond to thefield of the infrared detector in which the sighting device is used. Thelaser beam 1014 will then follow the periphery of the target zone of theinfrared detector (not shown). Once the motor 1021 is turned off, thereturn spring 1019 will cause the laser 1012 to center. In this manner,the central laser beam 1014 also (seen in FIG. 18 at₁₃ 1406) will now bein the center of the target zone. This serves as a calibration for theuser and insures that the laser sighting device is properly aimed.

A modified version of the laser sighting device of FIG. 11 isillustrated in FIG. 12. Laser sighting device 1100 is shown incombination with an infrared detector 1162 which has an infrared fieldof view 1161. Laser sighting device 1100 includes a laser 1112 whichprojects a laser beam 1114. Laser 1112 is pivotally mounted on pivot1120. A counterbalance 1115 is provided on the side of the laser 1112opposite the pivot 1115. The laser 1112 is powered by power source 1118and adapted to be rotated by motor 1121. Slip rings 1116 are providedfor facilitating the rotation of the laser 1112.

The laser sighting device 1100 of FIG. 12 is adapted to operate in thesame way as sighting device 1000 of FIG. 11. As the laser 1112 isrotated about the pivot point 1120, the laser beam 1114 is projectedagainst the target (not shown) about the periphery of the infrared fieldof view 1161 of the infrared detector 1162.

FIG. 13 illustrates yet another embodiment of the laser sighting deviceof the present invention. Laser sighting device 1200 is provided as astand-alone unit which may be mounted on and removed from standardinfrared detectors or radiometers. The sighting device 1200 includes alaser 1212 container within the housing 1201 of the sighting device1200. Laser 1212 is adapted to project a laser beam 1214 against atarget (not shown). The laser 1212 is powered by a power source (notshown). A motor 1221 is connected tot he laser 1212 by rotationalassembly 1227 thereby causing the laser to rotate within the housing1201. A slider 1226 is further provided to facilitate rotation of thelaser 1212 within the housing.

Adjustment screw 1217 is further provided for controlling the positionof the motor 1221 and, as such, the direction of the laser beam 1214. Aswivel ball 1222 is provided about the outward end of the laser 1212which is seated in swivel ball seat 1220. Spring washer 1218 is furtherprovided adjacent the swivel ball 1222.

The laser sighting device 1200 operates in substantially the same manneras the sighting devices depicted in FIGS. 11-12 in that he single laser1212 is rotated by motor 1221 to cause the projecting laser beam tocircle around the periphery of an infrared field.

FIGS. 14-16 illustrate yet another version of the laser sighting deviceof the present invention shown in combination with a radiometer. In theembodiment of FIGS. 14-16, a conventional radiometer 1300 is provided.The radiometer includes a telescope aiming sight 1305 with a lens 1306mounted on the top thereof. Telescope aiming sight 1305 permits the userto aim the radiometer 1300 against a target.

At least two laser sighting devices 1312 are provided on opposite sidesof the radiometer 1300. Device 1312 includes a pair of lasers 1314provided within the laser sighting devices 1312 positioned on each sideof the radiometer approximately 180 degrees apart which are adapted toproject a pair of laser beams (not shown) toward a target on either sideof the energy zone to be measured by the radiometer. In this manner, thelaser beams are used to define the outer periphery of the energy zonebeing measured by the radiometer 1300.

In an alternate embodiment, the lasers depicted in FIGS. 11-16 may bepulsed on and off in a synchronized manner. FIG. 17 depicts the seriesof intermittent lines that serve to outline the energy zone in such anembodiment. The intermittent use of the laser in this embodiment resultsin an increase in the efficiency of the laser, which, in turn, allowsfor an increased concentration of the laser's total wattage in a smallerarea, causing a brighter beam.

FIGS. 18 and 19 illustrate yet another and preferred best mode versionof the laser sighting device of the present invention, in combinationwith a radiometer. In this embodiment, a conventional radiometer 1400 isprovided. A laser sighting device denoted generally by reference numeral1401 has a single-beam laser generator 1402 which produces the laserbeam 1403. Aligned axially with the laser beam 1403, and in front of thelaser generator 1402, there is positioned a support 1404 housing anoptical means such as a beam splitter, holographic component or adiffraction grating 1405. In this instance, the diffraction grating 1405is selected when struck by the laser beam 1403 to produce, from theentering single beam 1403, a total of twelve sub-division beams 1403 awhich are symmetrically divergent about the axis and central beam 1406.Referring to FIG. 19 there is shown the pattern of laser light spots1403 b which are formed at individual mutually spaced locations, wherethe sub-division beams 1403 a strike the target 1407 whose temperatureis to be investigated. Due to the nature of the diffraction grating1405, spots 1403 b are circumferentially equidistantly spaced bydistance B in a circle about the axis of the laser beam 1403, and thetotal spread of the sub-division beams 1403 a is a width A which dependsupon the axial distance of the device from the target 1407. Adjacent toand laterally of the laser generator 1402 in its support 1404 there ispositioned a radiometer 1400 whose viewing axis is parallel to the axisand central beam 1406 of the generated laser beams 1403 a, but which mayif desired be made adjustable with respect to the axis and central beam1406 so that a selected area of the target, perhaps not at the center ofthe dots 1403 b, may be investigated.

The apparatus of any one of FIGS. 2, 3, 4, 6, 8, 11, 12, 13 and 18 mayfurther include means for projecting a laser beam axially to strike thesurface zone to be measured, e.g. in FIG. 18 the diffraction grating1405 would be selected to provide not only the sub-division beams 1403a, but also a central sub-division beam along the axis 1406.

Referring to FIG. 20, there is shown schematically a modificationwherein the radiometer 1400 is situated on the central longitudinal axisof the laser generator 1401 and within said plurality of laser beams ata suitable distance downstream of the diffraction grating so as not tointerference with the transmission of the sub-division beams to form thepattern of spots.

In a practical form of construction, the laser beam generator 1401 andthe diffraction grating support 1404 and the radiometer wouldconveniently be carried on a support structure, not shown, to provide ahand-held apparatus aimed at a selected area, or areas, to beinvestigated. Thus a method of identifying the extent of a radiationzone on a region whose temperature is to be measured may comprise thesteps of providing a sighting device for use in conjunction with saidradiometer, said device including means for generating a laser beam,splitting said laser beam into a plurality of three or more componentsby passing said beam through or over diffraction grating means, anddirecting said beam components towards said region so as to form aplurality of illuminated areas on said region where said beam componentsimpinge on said region, and determining temperature at said region withsaid radiometer. Preferably, the diffraction grating means is such as tocause the laser beam to be sub-divided into a plurality of three or morebeams which form illuminated areas arranged at intervals on a circle orother closed geometric figure on the region.

Having thus described the invention with particular reference to thepreferred forms thereof, it will be obvious that various changes andmodifications can be made therein without departing from the spirit andscope of the present invention as defined by the appended claims.

We claim:
 1. Device for temperature measurement comprising: a detectorfor receiving heat radiation emanating from a measurement spot on anobject of measurement; and a laser sighting system for said detectorcomprising a laser and a beam splitter, aligned to be illuminated bysaid laser, to produce a pattern of more than two separate spots on theobject of measurement in the form of a circular light intensitydistribution, identifying the position and size of the measurement spotby visible light to facilitate measurement.
 2. Device according to claim1 which includes a diffraction beam splitter.
 3. Device according toclaim 1 in which three or more light spots are arranged to form acircular pattern around a central spot to identify the target area. 4.Temperature measurement device comprising the combination of an infrareddetector having a field of view and a laser beam sighting systemcomprising a laser and a beam splitter illuminated by a single beam fromsaid laser and emitting more than two divergent laser beams split fromsaid single beam and projected onto a measurement surface area to form acircular pattern of visible spots mutually spaced apart to indicate tothe user the edge of the field of view of said detector.
 5. Deviceaccording to claim 4 in which said more than two split beams areprojected onto both the edge and also the center of the field of view ofthe detector to form a light intensity target pattern on the surface ofthe object of measurement.
 6. In a hand held non-contact temperaturemeasurement instrument comprising on a common support the combination ofan infrared radiation detector and a laser system for aiming saiddetector, in which said system includes a laser and an optical means:the improvement in which said optical means converts a single laser beamfrom said laser into more than two visible separated laser light spotsdisplayed in a pattern on a target surface to identify the edge of thearea on said surface from which infrared radiation is detected by saiddetector.
 7. The instrument of claim 6 in which the optical means is adiffraction lens.